      subroutine watput(n,m,xo,line)
c
c want to write a pdb file for a set of points. this subroutine 
c composes one line.
c 
      dimension xo(3)
      character*80 line
      character*5 wnum
      character*3 cnum
      character*8 pnum
      integer n,m
c
c n=atom number, m=residue number, xo=position
c
      line=" "
      line(1:6)="ATOM  "
      line(18:20)="SP "
      line(14:14)="O"
      write (wnum,310) n
      line(7:11)=wnum
      write (cnum,320) m
      line(24:26)=cnum
      write (pnum,330) xo(1)
      line(31:38)=pnum
      write (pnum,330) xo(2)
      line(39:46)=pnum
      write (pnum,330) xo(3)
      line(47:54)=pnum
310   format(i5)
320   format(i3)
330   format(f8.3)
c
      return
      end
